Forum Discussion
- The 2017 F450 ran up the Ike with 30,000 lbs in tow and didn't do much better than this 2020 Duramax. Does anyone remember if we discussed this run and if we came up with an excuse for why it didn't do better? About 11:30. I think the 2017 Powerstroke has fairly similar power ratings as the 2020 Duramax, 440 hp and 925 lbft. It was a little warmer out at 55F.
F450 with 30,000 lbs in tow ShinerBock wrote:
I think the Ram will be slightly worse than GM's time at around 12:00 minutes. Although I would like to see this test ran in 80F because I have a feeling it would significantly change the time of the Ford while not changing the GM and Ram times too much.
So you're thinking a poor performing turbo was the reason for the Duramax's terrible performance on this run and now you think the Cummins is going to do even worse? Does the Cummins have a turbo issue as well?RoyJ wrote:
Again, watch Gale Banks explain the limit of the stock L5P turbo. To go above the stock max power at sea level, essentially you have to "choke" your turbine side by activating the variable geometry nozzles at WOT (to gain turbo rpm, and therefore CFM), which is not within OEM GM parameters.
Doing that would create a lot of drive pressure and you would likely pop a head gasket before you had turbo failure. Not to mention a restriction like that would cause extremely high EGT's. It does not make sense to do this because you will not be able to make more power for any real period of time.
I know back when I had the stock VG turbo on my 2014 Cummins, I had the VGT vane position on my monitor. Both in stock form and after being tuned, going WOT the vanes would restrict to about 50% or so for a few seconds to get the wheel turning and then go fully open.ShinerBock wrote:
^^^That is not how turbos work. Air density, blade profile, A/R ratio, flow, blade size and other things dictate how much power a turbocharged engine looses at altitude. Turbo shaft speed generally increases with altitude to compensate for the decrease in air density. Bigger turbo wheels that make a lot of power cannot spool as fast as a smaller turbo wheel. So generally a smaller turbo that is at its max potential at sea level will do better at altitude than a larger turbo.
Also, tuners do not often push turbos way past their efficiency zones, at least not a good one. If you go past the turbos efficiency zone then you start making less power and higher EGT's which is not what you want so to make the best gains you have to stay withing the turbo's efficiency. A tuner will generally keep adding fuel and timing until they start to see power numbers start to decrease with excessive EGT's. That is the point where they know the turbo is leaving it's efficiency zone and a bigger turbo is needed to make more power so they back the fuel and timing back down to where it made more power. Diesels are regulated by fuel and not air like gas engines.
Re-read what I wrote, it does not contradict anything you said.
A turbo that is sized to produce full rated power at sea level would start to starve the engine of CFM at higher altitude. Because maintaining the same absolute manifold pressure at altitude, is similar to over-boosting at sea level (higher pressure ratio), which almost ALWAYS pushes you to a lower eff curve on the compressor map.
Again, watch Gale Banks explain the limit of the stock L5P turbo. To go above the stock max power at sea level, essentially you have to "choke" your turbine side by activating the variable geometry nozzles at WOT (to gain turbo rpm, and therefore CFM), which is not within OEM GM parameters.- ^^^Theoretically and based on the Ford's performance the Ram should do the run in 10 minutes 50 seconds.
- I think the Ram will be slightly worse than GM's time at around 12:00 minutes. Although I would like to see this test ran in 80F because I have a feeling it would significantly change the time of the Ford while not changing the GM and Ram times too much.
- Shiner, what do you think the results of the RAM will be with it's old school 6 speed? Hopefully the conditions will be similar when they finally test it.
- It is not so much as a "fix" for a turbo, but rather making it perform better in a certain situations, however, this may take away from how it performs in other situations. Making it better for lower altitudes may decrease its performance for higher altitudes. Making it spool quicker at lower rpm may reduce top end performance. Having an air to water to air intercooler may reduce lag and improve off the line performance, but it will reduce sustained performance especially in hotter temps. It is a give and take and I doubt GM or any manufacturer designs their turbos just to post the best possible time on the Ike. you also have to throw emissions into the mix.
This is likely the reason why Ford has went through four different turbos on the 6.7L since 2011. - So let's, at least in our mind, fix the GM turbo and rerun the test. Let's assume the GM performs as it should and gets to the top in 9 minutes 55 seconds. The Ford gets to the top in the exact same time as before ... 10 minutes 20 seconds. Are we still happy with the results of the Ford?
4x4ord wrote:
ShinerBock wrote:
4x4ord wrote:
If the GM had performed the way it should have people would have making excuses for why the Ford took so long getting to the top. Probably someone would have been blaming the turbo.
That is probably because the turbo and intake system plays a huge factor in how much power a diesel can make and sustain. If you put different turbos on the exact same engine/drivetrain and take it up the Ike, the results may be vastly different depending on how diverse the turbos and the intake systems are.
What I'm getting at is had the GM not had issues it would have run up the mountain in under 10 minutes. It really should have beaten the Ford. Had that happened fingers would have been pointing at why Ford's 475 HP engine couldn't keep up with a 445 hp Duramax.
And pointing to the turbo and intake system would be a legitimate argument since it is this system that dictates how much of that 475 hp or 445 hp is lost at altitude. People tend to think that the amount of power a turbocharged engine looses is static with all turbocharged engines. It is not and it depends on the turbo configuration. Some configurations may loose more than others or get hotter sooner because of overspeeding not allowing it to sustain the power levels. Some may be more effected to outside temps and others may not meaning that if the temps were higher(say 80F) then the GM could likely do just slightly worse while the Ford does significantly worse. I am not saying this is or will be the case, I am just using it as an example.
